| Ethylene and propylene are the primary stock of the petroleum chemical industries.With the dwindling of oil,the new method with broad attentions is that firstly produce methanol from coal or natural gas as raw materials,then methanol is produced into low-carbon olefins like ethylene and propylene(methanol-to-olefin,MTO),which is expected to replace the method of making olefins from naphtha olefin.In the new process of MTO,the research on the structure and efficiency of the reaction cracking furnace and demethanizer is the most important part.In this paper,simulation studies and the analysis for rational use of energy of MTO were carried out based on the existing data,especially for the demethanizer by oil-absorption.Aspen Plus simulation software was firstly used to simulate a MTO process,especially the absorption process in the demethanizer.The parameters that required in the simulation procedure were obtained.Other simulation of demethanizer using the cryogenic separation process that applied in a ethylene process was also discussed in the paper and compared with simulation of the oil-absorption demethanizer.The separation results showed that based on their own suitable operation condition such as pressure and temperature,fewer methane and hydrogen,as well as higher ethylene and propylene were found in the simulation of MTO process;on the other hand,the oil-adsorption demethanizer has less lost of ethylene than the cryogenic separation demethanizer from the yield and cost of energy.Then,the exergy and thermodynamic efficiency calculation for the two demethanizers were launched by the equations of entropy and exergy following the simulation.The results appeared that the highest thermodynamics efficiency in oil absorption demethanizer was 56%while the number in cryogenic separation demethanizer was 70%.The thermodynamics efficiencies for other towers in separation procedure of MTO were also calculated and the results were likely to be used for innovation of MTO industry. |
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